Part 12 - Load Effective Address

For a complete table of contents of all the lessons please click below as it will give you a brief of each lesson in addition to the topics it will cover. https://github.com/mytechnotalent/Reverse-Engineering-Tutorial

When a binary executes in RAM the OS will unmap the code into a data segment where it finds free space in memory. 

Load Effective Address loads a given memory address as a pointer to any given variable. For example:

lea rbx, my_var

This will load the address of my_var  into rbx. 

In C++, a pointer actually adds what the user would see as one if something was incremented however it is actually moving it 2 bytes forward under the hood assuming it is a word in length or 16 bits or 2 bytes. Same thing.

In Assembly every single byte is addressable. For example:

lea rax, my_var

inc rax

mov word ptr [rax], rbx

Let’s say the value of 0x20 is in rbx. This above instruction will place the value of 0x20 into a non-word boundary which will result in an error. You would have to increment rax by 2 to ensure that does not happen.

Next week we will dive into the data segment! Stay tuned!